The meeting on Thursday aimed "to identify the most urgent needs within countries and match them with rapid international support," the WHO said.

"These steps align with recognition of the extraordinary measures needed, on a massive scale, to contain the outbreak in settings characterised by extreme poverty, dysfunctional health systems, a severe shortage of doctors, and rampant fear."

International agencies are looking into emergency food drops and truck convoys to reach people in Liberia and Sierra Leone cordoned off from the outside world to halt the spread of the virus, a top World Bank official said.

Medicins Sans Frontieres president Joanne Liu says it will take about six months to bring the epidemic under control and called on WHO to take a greater leadership role.

She said controlling the outbreak is vital, especially in Liberia where the president declared a state of emergency earlier this month.

"They need right now help, they need leadership, coordination," she said.

"They will not be able to overcome that by themself. If we don't stabilise Liberia, we'll never stabilise the whole region."

Countries declare health emergency

Guinea has declared a public health emergency and is sending health workers to all affected border points, an official said.

An estimated 377 people have died in Guinea since the outbreak began in March in remote parts of a border region near Sierra Leone and Liberia.

Guinea says its outbreak is under control with the numbers of new cases falling, but the measures are needed to prevent new infections from neighbouring countries.

The experimental Ebola treatment was developed by US company Mapp Biopharmaceutical based on years of US and Canadian research. Read more.

"Trucks full of health materials and carrying health personnel are going to all the border points with Liberia and Sierra Leone," said Aboubacar Sidiki Diakit, president of Guinea's Ebola commission.

As many as 3,000 people are waiting at 17 border points for a green light to enter the country, he said.

"Any who are sick will be immediately isolated. People will be followed up on. We can't take the risk of letting everyone through without checks," he said.

Sierra Leone has declared Ebola a national emergency as has Liberia, which is hoping that two of its doctors diagnosed with Ebola can start treatment with some of the limited supply of experimental drug ZMapp.

Canada's Tekmira Pharmaceuticals Corp is also exploring making more of its experimental Ebola treatment, chief executive officer Mark Murray said.

Nigeria also has declared a national emergency, although it has so far escaped the levels of infection seen in the three other countries.

Ebola is one of the world's most deadly diseases and kills the majority of those infected. Its symptoms include internal and external bleeding, diarrhoea and vomiting.

Epidemic puts strain on health services

Health experts say government responses to the disease need to be calibrated to prevent its spread, while avoiding measures that could induce panic or damage economies unnecessarily.

That task is harder because health services have been stretched to the breaking point and mistrust of health workers among some rural communities is high.

A Liberian government document seen by Reuters shows the strain on its health ministry as it confronts the emergency.

An Ebola call centre in Monrovia is struggling to keep up with the volume and needs more staff, telephone lines and a deputy supervisor, the Ministry of Health document said.

"The case investigation team only has one vehicle so they can't get out and then there's the issue of no space at the ETU (Ebola Treatment Unit) to bring patients," it said.

US president Barack Obama has discussed the outbreak with the presidents of Liberia and Sierra Leone, the White House said.

Families of US diplomats in Sierra Leone have been ordered to leave the country because of limitations on regular medical care as a result of the outbreak.

Ebola to impact economic growth: Moody's

Ratings agency Moody's says Ebola holds economic ramifications for some West African states as disruption to commerce, transport and borders lasts at least another month.

Among the signs of the regional economic impact, Ivory Coast will not allow any ships from Guinea, Sierra Leone and Liberia to enter its port at Abidjan, according to a port statement.

Fewer passengers are arriving at Ivory Coast's main airport from Freetown, Conakry and Monrovia because of the virus leading to a shortfall of about 4,000 passengers a month, Abdoulaye Coulibaly, chairman of Air Cote d'Ivoire, told Reuters.

Ivory Coast and its eastern neighbour, Ghana, have recorded no cases of Ebola.

Ghana's government says it will increase its funding for preventative health and impose a moratorium on international conferences for three months as a precaution.